1. Field of the Invention
The present invention relates generally to ear plugs. More specifically, the present invention relates to an ear plug comprising a shell with at least two electrodes adapted for measuring brain wave signals, said electrodes being connected with means for processing the measured signals. The invention further relates to a method of producing an ear plug.
It is generally known, particularly within medical science, to measure brain waves by placing electrodes on the scalp of a subject, whose brain waves it is desired to measure (for simplicity denoted “subject” in the following), and to view, process and interpret the measured brain waves using suitable equipment. Typically, such equipment is an electroencephalograph, by means of which a so-called electroencephalogram (EEG) may be achieved. The EEG is obtained by a measurement and recording of electrical activity in a subject's brain by measuring the electric potential generated on the surface of the subject's scalp by currents flowing between dendrites in the subject's brain. Within medical science EEG's are used for various diagnostic purposes.
2. The Prior Art
A system for such a use is known from WO-A1-2006/047874, which describes measurement of brain waves by use of electrodes placed in connection with at least one of the ears of the subject, i.e. placed on an outer ear part or placed in the ear canal. The measurements are used particularly for detecting the onset of an epileptic seizure. WO-A1-2006/047874 also describes the use of electrodes in pairs as detection and reference electrodes respectively, such a setup being well known in the field of electroencephalography.
Furthermore it is known from WO-A1-2008/116462 to measure the hearing ability of the subject by using a hearing aid to generate a test stimulus signal and transmit said signal to a subject as an acoustic stimulus, and by detecting a brain wave response to said acoustic stimulus signal by use of separate electrodes placed on the subject's scalp and transmitting the brain wave response to an electrophysiological instrument such as an electroencephalograph for processing.
WO-A1-2007/047667 describes an ear plug for measuring EEG-signals. The ear plug comprises an exterior shell with electrodes, the shell being made of a soft, compressible material, such as memory foam, capable of conforming to the interior of an individual's auditory canal. The signals obtained with the ear plug are transmitted to external units for processing and monitoring.
However, at least the signal processing devices of the known systems are, due to their complexity and use of extensive and complicated equipment, confined to use and operation by qualified staff. Furthermore the placement of in by far most cases electrodes and in any case associated wiring on various parts of the subject's scalp and/or head renders the known systems rather unattractive for use outside laboratory surroundings, thus rendering exploitation of the advantages related to the use of brain wave measurements outside the laboratory, e.g in everyday use, rather cumbersome.
With the ear plug according to WO-A1-2007/047667 a solution to the problem regarding the electrodes is proposed. However, several disadvantages remain. There is a risk of insufficient contacting between the ear canal and the electrodes due to the shell, which again may cause poor or insufficient signal quality. Also, the shell properties imply a low durability of the proposed ear plug. Furthermore, it is well known, that ear plugs of the type proposed in WO-A1-2007/047667 cause an enlarged risk of the user suffering from occlusion and/or insufficient ventilation of the ear canal, particularly during long term use.